Experimental and analytical study of ultrasonic micro powder feeding

Experimental and theoretical studies were carried out to understand an ultrasonic micro dry powder feeding mechanism. The ultrasonic micro feeding system was used to deliver ultra-fine dry powders through capillary tubes with an inner diameter of 125??m and 50??m, respectively. The powder flow rates were measured and various powders were discharged continuously at a flow rate as low as 10??g?s?1. The powder packing inside the capillary tube was densified by the ultrasonic waves since the powder density at the feeding tip was much higher than that in the hopper. Acoustic streaming and friction driving might be the driving forces for the powder feeding through the micro capillary tubes. Further theoretical study will be needed to fully understand the behaviour of this feeding mechanism. It was also found that thermal effects in the lead zirconate titanate plate influenced the performance of powder feeding significantly. With this system, micro dry powder patterns can be deposited directly and precisely on substrates.

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